Planters are used for planting seeds (e.g., corn, soybeans) in a field. On smaller planters, a farmer fills a seed hopper on every individual row unit of the planter. Multiple row units are mounted side-by-side along a single toolbar. At each row unit the seeds are fed from the hopper to a meter on the row unit, which meters seeds one by one into the trench opened by the row unit.
With larger planters (having, e.g., 48 row units) it has become common practice to have two side-by-side bulk hoppers. A blower blows seed from the bulk hoppers out to the individual row units through a plurality of lines. This cuts down the time per filling operation and the number of filling operations. Since the left hopper feeds one half of the row units and the right hopper feeds the other half, a farmer can fill one hopper with seed type A and the other hopper with seed type B and then see which seed type results in better performance and yield.